how to help a shy girl being less introvert

hello, so, there is this girl in my class, she is very shy and litteraly NEVER talk (i mean it). i tried to be friends with her, asked about her hobbies and all. But she dont have any hobbies, dont listen to music, dont do anything besides school and also dont watch any movies, dont play any games and all...... and she makes me very sad because she looks always stressed out, her leg is always shaking when she sit down. I used to be like this, so i want to help her but without being too.....invasive ? Also she barely answers when i (and my classmates) talk to her. I tried to talk to her about everything : school, video games, life in general, even about myself so she could feel more comfortable ? But she always answers "oh!...." and "yeah..." or "okay..." but she always looks insecure. It is really unfortunate because she looks really kind. She always follows a girl in my class but they dont even talk together. How can i help her being less shy and talk more ? How could i maybe make her more confident ? I dont really know if its a good idea BUT yeah.. please help